NEW YORK — The courtroom outburst of a supporter of a terrorist group is evidence that he deserves his 20-year prison term for plotting a New Year's Eve machete attack in upstate New York, an appeals court concluded as it rejected his claims Thursday that the sentence is unfair.

Emanuel Lutchman, 28, appealed the sentence he received last year after he pleaded guilty to conspiring to provide material support to a foreign terrorist organization, the Islamic State group, sometimes referred to as "ISIL."

He maintained through his lawyer that the length of his punishment was unfair because the plot relied on the assistance and participation of government operatives and because of his mental illness. Federal authorities and informants thwarted Lutchman's planned December 2015 knife and machete attack at the Merchants Grill in Rochester.

The 2nd U.S. Circuit Court of Appeals, in a decision written by Judge Dennis Jacobs, concluded that Lutchman's sentence, the maximum allowable, was reasonable.

The three-judge appeals panel cited Lutchman's behavior at his sentencing, saying it validated U.S. District Judge Frank Geraci's decision to give him two decades in prison despite Lutchman's claims before sentencing that he had moved on from a radical Islamic ideology.

"Lutchman had maintained a pretense of remorse that was dropped after the sentence was announced. Lutchman then laughed, reaffirmed his allegiance to ISIL's leader, and stated that more individuals like him would 'rise up,'" the 2nd Circuit noted.

The outburst prompted Geraci to boost Lutchman's supervised release from 30 years to 50 years.

Prior to sentencing, Lutchman blamed the plot in part on his history of mental illness and "abandonment issues." Lutchman was a former gang member who converted to Islam while in prison for a 2006 robbery conviction and was influenced by other inmates' religious extremism, his lawyer said in court documents prior to sentencing.

Lutchman's lawyer did not immediately respond to a request for comment.